Coenzyme Q.sub.10 is a class of physiological substances occurring as component factors of the mitochondrial electron transfer system within the biological cell. Coenzyme Q.sub.10 acts directly as an electron carrier in the oxidative phosphorylation reactions, through metabolic pathways, particularly aerobic pathways, to produce ATP and hence energy.
It seems that the demand for coenzyme Q.sub.10 is increased in normal subjects in the state of severe physical fatigue and patients with cardiovascular disease, chronic debilitating disease, or on prolonged pharmacotherapy. It has been shown that a deficiency of coenzyme Q.sub.10 occurs particularly in ischemic heart diseases, senile myocardial sclerosis, and hypertensive heart diseases. Therefore, it is a sound therapeutic choice to administer coenzyme Q.sub.10 to those patients.
Moreover, coenzyme Q.sub.10 has been used for non-therapeutic purposes as a nutrient or nutritional supplement just like vitamins.
In order that coenzyme Q.sub.10 may express its therapeutic efficacy or nutritional effect, it is most important to increase the coenzyme Q.sub.10 level within the patient's tissue cells.
Coenzyme Q.sub.10 is a lipid-soluble and practically water-insoluble substance and, therefore, it is only sparingly soluble in gastric juice. Consequently, oral dosage forms containing coenzyme Q.sub.Q.sub.10 in solid state, such as tablets, granules, capsules, and suspensions for extemporaneous preparation, are not well absorbed after oral administration. This means that a considerably greater amount of coenzyme Q.sub.10 than actually needed must be administered to the patient but such a practice tends to cause adverse gastrointestinal reactions such as epigastric discomfort, anorexia, nausea, and diarrheas.
Much research has heretofore been undertaken for overcoming those disadvantages. Japanese Kokai Publications Sho-55-81813 and Sho-61-221131, among others, disclose coenzyme Q.sub.10 formulations of the solution type or the emulsion/dispersion type. However, such pharmaceutical devices are not sufficient to improve the absorption of coenzyme Q.sub.10 in a satisfactory measure.
Japanese Kokai Publication Sho-56-18914 discloses a technology for accelerating the lymphatic absorption of coenzyme Q.sub.10. This technology has been demonstrated to increase the absorption of coenzyme Q.sub.10 in a certain measure but has not proved practically useful as yet.
Japanese Kokai Publication Sho-60-89442 discloses a cyclodextrin-clathrated coenzyme Q.sub.10 formulation. Japanese Kokai Publication Sho-60-1124 discloses a coenzyme Q.sub.10 -containing ribosomal formulation. However, those coenzyme Q.sub.10 preparations require a complicated pharmaceutical procedure for production and are not practically fully satisfactory.
Italian Patent 1190442 Specification discloses a technology which, instead of using coenzyme Q.sub.10 as such, comprises converting a reduced form of coenzyme Q.sub.10 to a derivative such as an acyl ester, a sulfuric acid ester, or a phosphoric acid ester and administering this coenzyme Q.sub.10 derivative for enhanced absorption. However, the effect of the technology has not been supported by experimental data.